Method and apparatus for supplying energy to a medical device

ABSTRACT

An apparatus configured to control transmission of wireless energy supplied to an electrically operable medical device adapted to be implanted in a mammal patient is provided. The apparatus comprises an external energy source adapted to be located outside the mammal patient and comprising an external control unit, the external energy source being adapted to transmit wireless energy, and an internal energy receiver located inside the patient and comprising an internal control unit, the internal energy receiver being adapted to receive the wireless energy, the internal energy receiver being configured to directly or indirectly supply wirelessly received energy to the electrically operable medical device, and a control unit comprising the internal control unit or the external control unit, wherein the electrically operable medical device is adapted to transfer control information to the control unit, the control information being related to an energy adapted for operating the medical device and said control information being adapted to be used to control the receipt of energy.

TECHNICAL FIELD

The present invention relates generally to a method and apparatus forsupplying wireless energy to a medical device implanted in a patient. Inparticular, the invention is concerned with controlling the amount ofenergy transferred from an energy source outside the patient to anenergy receiver inside the patient.

BACKGROUND

Medical devices, designed to be implanted in a patient's body, aretypically operated by means of electrical power. Such medical devicesinclude electrical and mechanical stimulators, motors, pumps, etc, whichare designed to support or stimulate various body functions. Electricalpower can be supplied to such an implanted medical device from alikewise implanted battery or from an external energy source that cansupply any needed amount of electrical power intermittently orcontinuously without requiring repeated surgical operations.

An external energy source can transfer wireless energy to an implantedinternal energy receiver located inside the patient and connected to themedical device for supplying received energy thereto. So-called TET(Transcutaneous Energy Transfer) devices are known that can transferwireless energy in this manner. Thereby, no leads or the likepenetrating the skin need to be used for connecting the medical deviceto an external energy source, such as a battery.

A TET device typically comprises an external energy source including aprimary coil adapted to inductively transfer any amount of wirelessenergy, by inducing voltage in a secondary coil of an internal energyreceiver which is implanted preferably just beneath the skin of apatient. The highest transfer efficiency is obtained when the primarycoil is positioned close to the skin adjacent to and in alignment withthe secondary coil, i.e. when a symmetry axis of the primary coil isparallel to that of the secondary coil.

Typically, the amount of energy required to operate an implanted medicaldevice may vary over time depending on the operational characteristicsof the device. For example, the device may be designed to switch on andoff at certain intervals, or otherwise change its behavior, in order toprovide a suitable electrical or mechanical stimulation, or the like.Such operational variations will naturally result in correspondingvariations with respect to the amount of required energy.

Furthermore, the position of the external energy source relative to theimplanted internal energy receiver is a factor that affects theefficiency of the energy transfer, which highly depends on the distanceand relative angle between the source and the receiver. For example,when primary and secondary coils are used, changes in coil spacingresult in a corresponding variation of the induced voltage. Duringoperation of the medical device, the patient's movements will typicallychange the relative spacing of the external source and the internalreceiver arbitrarily such that the transfer efficiency greatly varies.

If the transfer efficiency becomes low, the amount of energy supplied tothe medical device may be insufficient for operating the deviceproperly, so that its action must be momentarily stopped, naturallydisturbing the intended medical effect of the device.

On the other hand, the energy supplied to the medical device may alsoincrease drastically, if the relative positions of the external sourceand the internal receiver change in a way that unintentionally increasesthe transfer efficiency. This situation can cause severe problems sincethe implant cannot “consume” the suddenly very high amount of suppliedenergy. Unused excessive energy must be absorbed in some way, resultingin the generation of heat, which is highly undesirable. Hence, ifexcessive energy is transferred from the external energy source to theinternal energy receiver, the temperature of the implant will increase,which may damage the surrounding tissue or otherwise have a negativeeffect on the body functions. It is generally considered that thetemperature in the body should not increase more than three degrees toavoid such problems.

It is thus highly desirable to always supply the right amount of energyto an implanted medical device, in order to ensure proper operationand/or to avoid increased temperature. Various methods are known forcontrolling the amount of transferred energy in response to differentconditions in the receiving implant. However, the presently availablesolutions for controlling the wireless transfer of energy to implantedmedical devices are lacking in precision in this respect.

For example, U.S. Pat. No. 5,995,874 discloses a TET system in which theamount of transmitted energy from a primary coil is controlled inresponse to an indication of measured characteristics of a secondarycoil, such as load current and voltage. The transmitted energy can becontrolled by varying the current and voltage in the primary coil,transmission frequency or coil dimensions. In particular, a change iseffected in the saturation point of the magnetic field between thecoils, in order to adjust the power transfer efficiency. However, it isnot likely that this solution will work well in practice, since asaturation point in the human tissue would not occur, given the magneticfield levels that are possible to use. Moreover, if the energytransmission must be increased considerably, e.g. to compensate forlosses due to variations in alignment and/or spacing between the coils,the relatively high radiation generated may be damaging or unhealthy orunpleasant to the patient, as is well known.

An effective solution is thus needed for accurately controlling theamount of transferred energy to an implanted medical device to ensureproper operation thereof. Moreover, excessive energy transfer resultingin raised temperature at the medical device, and/or power surges shouldbe avoided, in order to avoid tissue damages and other unhealthy orunpleasant consequences for the patient.

SUMMARY

A method is thus provided for controlling transmission of wirelessenergy supplied to an electrically operable medical device implanted ina mammal patient. The wireless energy is transmitted by means of aprimary coil in an external energy source located outside the patientand received inductively by means of a secondary coil in an internalenergy receiver located inside the patient. The internal energy receiveris connected to the medical device for directly or indirectly supplyingreceived energy thereto. Feedback control information is transferredfrom the secondary coil to the primary coil by switching the secondarycoil on and off to induce a detectable impedance load variation in theprimary coil encoding the feedback control information. The feedbackcontrol information relates to the energy for operating the medicaldevice and is used for controlling the transmission of wireless energyfrom the external energy source.

An apparatus is also provided for controlling transmission of wirelessenergy supplied to an electrically operable medical device implanted ina mammal patient. The apparatus comprises an external energy sourceadapted to transmit the wireless energy by means of a primary coil whenlocated outside the patient, and an internal energy receiver adapted toreceive the transmitted wireless energy inductively by means of asecondary coil when located inside the patient, and to directly orindirectly supply received energy to the medical device. The internalenergy receiver is further adapted to transfer feedback controlinformation from the secondary coil to the primary coil in accordancewith the above method.

The method and apparatus may be implemented according to differentembodiments and features as follows:

In one embodiment, an internal control unit controls the on and offswitching of the secondary coil, wherein the feedback controlinformation may include at least one predetermined parameter relating tothe received energy. The predetermined parameter may also be variable.The feedback control information may also relate to the received energyand require artificial intelligence to be generated. An implantableswitch may be used to execute the on and off switching of the secondarycoil as controlled by the internal control unit. The switch may be anelectronic switch such as a transistor. Further, the internal controlunit may comprise a memory for storing the transferred feedback controlinformation.

In another embodiment, an internal control unit determines an energybalance between the energy received by the internal energy receiver andthe energy used for the medical device, where the feedback controlinformation relates to the determined energy balance. An externalcontrol unit then controls the transmission of wireless energy from theexternal energy source based on the determined energy balance and usingthe feedback control information.

In yet another embodiment, an external control unit determines theenergy balance above based on the feedback control information, in thatcase comprising measurements relating to characteristics of the medicaldevice, and controls the transmission of wireless energy from theexternal energy source based on the determined energy balance and usingthe feedback control information.

A change in the energy balance may be detected to control thetransmission of wireless energy based on the detected energy balancechange. A difference may also be detected between energy received by theinternal energy receiver and energy used for the medical device, tocontrol the transmission of wireless energy based on the detected energydifference.

When controlling the energy transmission, the amount of transmittedwireless energy may be decreased if the detected energy balance changeimplies that the energy balance is increasing, or vice versa. Thedecrease/increase of energy transmission may further correspond to adetected change rate.

The amount of transmitted wireless energy may further be decreased ifthe detected energy difference implies that the received energy isgreater than the used energy, or vice versa. The decrease/increase ofenergy transmission may then correspond to the magnitude of the detectedenergy difference.

As mentioned above, the energy used for the medical device may beconsumed to operate the medical device, and/or stored in at least oneenergy storage device of the medical device.

In one alternative, substantially all energy used for the medical deviceis consumed to operate the medical device. In that case, the energy maybe consumed after being stabilized in at least one energy stabilizingunit of the medical device.

In another alternative, substantially all energy used for the medicaldevice is stored in the at least one energy storage device. In yetanother alternative, the energy used for the medical device is partlyconsumed to operate the medical device and partly stored in the at leastone energy storage device.

The energy received by the internal energy receiver may be stabilized bya capacitor, before the energy is supplied directly or indirectly to themedical device.

The difference between the total amount of energy received by theinternal energy receiver and the total amount of consumed and/or storedenergy may be directly or indirectly measured over time, and the energybalance can then be determined based on a detected change in the totalamount difference.

The energy received by the internal energy receiver may further beaccumulated and stabilized in an energy stabilizing unit, before theenergy is supplied to the medical device. In that case, the energybalance may be determined based on a detected change followed over timein the amount of consumed and/or stored energy. Further, the change inthe amount of consumed and/or stored energy may be detected bydetermining over time the derivative of a measured electrical parameterrelated to the amount of consumed and/or stored energy, where thederivative at a first given moment is corresponding to the rate of thechange at the first given moment, wherein the rate of change includesthe direction and speed of the change. The derivative may further bedetermined based on a detected rate of change of the electricalparameter.

The energy received by the internal energy receiver may be supplied tothe medical device with at least one constant voltage, wherein theconstant voltage is created by a constant voltage circuitry. In thatcase, the energy may be supplied with at least two different voltages,including the at least one constant voltage.

The energy received by the internal energy receiver may also be suppliedto the medical device with at least one constant current, wherein theconstant current is created by a constant current circuitry. In thatcase, the energy may be supplied with at least two different currentsincluding the at least one constant current.

The energy balance may also be determined based on a detected differencebetween the total amount of energy received by the internal energyreceiver and the total amount of consumed and/or stored energy, thedetected difference being related to the integral over time of at leastone measured electrical parameter related to the energy balance. In thatcase, values of the electrical parameter may be plotted over time as agraph in a parameter-time diagram, and the integral can be determinedfrom the size of the area beneath the plotted graph. The integral of theelectrical parameter may relate to the energy balance as an accumulateddifference between the total amount of energy received by the internalenergy receiver and the total amount of consumed and/or stored energy.

The energy storage device in the medical device may include at least oneof: a rechargeable battery, an accumulator or a capacitor. The energystabilizing unit may include at least one of: an accumulator, acapacitor or a semiconductor adapted to stabilize the received energy.

When the energy received by the internal energy receiver is accumulatedand stabilized in an energy stabilizing unit before energy is suppliedto the medical device and/or energy storage device, the energy may besupplied to the medical device and/or energy storage device with atleast one constant voltage, as maintained by a constant voltagecircuitry. In that case, the medical device and energy storage devicemay be supplied with two different voltages, wherein at least onevoltage is constant, maintained by the constant voltage circuitry.

Alternatively, when the energy received by the internal energy receiveris accumulated and stabilized in an energy stabilizing unit beforeenergy is supplied to the medical device and/or energy storage device,the energy may be supplied to the medical device and/or energy storagedevice with at least one constant current, as maintained by a constantcurrent circuitry. In that case, the medical device and energy storagedevice may be supplied with two different currents wherein at least onecurrent is constant, maintained by the constant current circuitry.

The wireless energy may be initially transmitted according to apredetermined energy consumption plus storage rate. In that case, thetransmission of wireless energy may be turned off when a predeterminedtotal amount of energy has been transmitted. The energy received by theinternal energy receiver may then also be accumulated and stabilized inan energy stabilizing unit before being consumed to operate the medicaldevice and/or stored in the energy storage device until a predeterminedtotal amount of energy has been consumed and/or stored.

Further, the wireless energy may be first transmitted with thepredetermined energy rate, and then transmitted based on the energybalance which can be determined by detecting the total amount ofaccumulated energy in the energy stabilizing unit. Alternatively, theenergy balance can be determined by detecting a change in the currentamount of accumulated energy in the energy stabilizing unit. In yetanother alternative, the energy balance, can be determined by detectingthe direction and rate of change in the current amount of accumulatedenergy in the energy stabilizing unit.

The transmission of wireless energy may be controlled such that anenergy reception rate in the internal energy receiver corresponds to theenergy consumption and/or storage rate. In that case, the transmissionof wireless energy may be turned off when a predetermined total amountof energy has been consumed.

The energy received by the internal energy receiver may be firstaccumulated and stabilized in an energy stabilizing unit, and thenconsumed or stored by the medical device until a predetermined totalamount of energy has been consumed. In that case, the energy balance maybe determined based on a detected total amount of accumulated energy inthe energy stabilizing unit. Alternatively, the energy balance may bedetermined by detecting a change in the current amount of accumulatedenergy in the energy stabilizing unit. In yet another alternative, theenergy balance may be determined by detecting the direction and rate ofchange in the current amount of accumulated energy in the energystabilizing unit.

Suitable sensors may be used for measuring certain characteristics ofthe medical device and/or detecting the current condition of thepatient, somehow relating to the amount of energy needed for properoperation of the medical device. Thus, electrical and/or physicalparameters of the medical device and/or physical parameters of thepatient may be determined, and the energy can then be transmitted with atransmission rate which is determined based on the parameters. Further,the transmission of wireless energy may be controlled such that thetotal amount of transmitted energy is based on said parameters.

The energy received by the internal energy receiver may be firstaccumulated and stabilized in an energy stabilizing unit, and thenconsumed until a predetermined total amount of energy has been consumed.The transmission of wireless energy may further be controlled such thatan energy reception rate at the internal energy receiver corresponds toa predetermined energy consumption rate.

Further, electrical and/or physical parameters of the medical deviceand/or physical parameters of the patient may be determined, in order todetermine the total amount of transmitted energy based on theparameters. In that case, the energy received by the internal energyreceiver may be first accumulated and stabilized in an energystabilizing unit, and then consumed until a predetermined total amountof energy has been consumed.

The energy is stored in the energy storage device according to apredetermined storing rate. The transmission of wireless energy may thenbe turned off when a predetermined total amount of energy has beenstored. The transmission of wireless energy can be further controlledsuch that an energy reception rate at the internal energy receivercorresponds to the predetermined storing rate.

The energy storage device of the medical device may comprise a firststorage device and a second storage device, wherein the energy receivedby the internal energy receiver is first stored in the first storagedevice, and the energy is then supplied from the first storage device tothe second storage device at a later stage.

When using the first and second storage devices in the energy storagedevice, the energy balance may be determined in different ways. Firstly,the energy balance may be determined by detecting the current amount ofenergy stored in the first storage device, and the transmission ofwireless energy may then be controlled such that a storing rate in thesecond storage device corresponds to an energy reception rate in theinternal energy receiver. Secondly, the energy balance may be determinedbased on a detected total amount of stored energy in the first storagedevice. Thirdly, the energy balance may be determined by detecting achange in the current amount of stored energy in the first storagedevice. Fourthly, the energy balance may be determined by detecting thedirection and rate of change in the current amount of stored energy inthe first storage device.

Stabilized energy may be first supplied from the first storage device tothe second storage device with a constant current, as maintained by aconstant current circuitry, until a measured voltage over the secondstorage device reaches a predetermined maximum voltage, and thereaftersupplied from the first storage device to the second storage energystorage device with a constant voltage, as maintained by a constantvoltage circuitry. In that case, the transmission of wireless energy maybe turned off when a predetermined minimum rate of transmitted energyhas been reached.

The transmission of energy may further be controlled such that theamount of energy received by the internal energy receiver corresponds tothe amount of energy stored in the second storage device. In that case,the transmission of energy may be controlled such that an energyreception rate at the internal energy receiver corresponds to an energystoring rate in the second storage device. The transmission of energymay also be controlled such that a total amount of received energy atthe internal energy receiver corresponds to a total amount of storedenergy in the second storage device.

In the case when the transmission of wireless energy is turned off whena predetermined total amount of energy has been stored, electricaland/or physical parameters of the medical device and/or physicalparameters of the patient may be determined during a first energystoring procedure, and the predetermined total amount of energy may bestored in a subsequent energy storing procedure based on the parameters.

When electrical and/or physical parameters of the medical device and/orphysical parameters of the patient are determined, the energy may bestored in the energy storage device with a storing rate which isdetermined based on the parameters. In that case, a total amount ofenergy may be stored in the energy storage device, the total amount ofenergy being determined based on the parameters. The transmission ofwireless energy may then be automatically turned off when the totalamount of energy has been stored. The transmission of wireless energymay further be controlled such that an energy reception rate at theinternal energy receiver corresponds to the storing rate.

When electrical and/or physical parameters of the medical device and/orphysical parameters of the patient are determined, a total amount ofenergy may be stored in the energy storage device, the total amount ofenergy being determined based on said parameters. The transmission ofenergy may then be controlled such that the total amount of receivedenergy at the internal energy receiver corresponds to the total amountof stored energy. Further, the transmission of wireless energy may beautomatically turned off when the total amount of energy has beenstored.

When the energy used for the medical device is partly consumed andpartly stored, the transmission of wireless energy may be controlledbased on a predetermined energy consumption rate and a predeterminedenergy storing rate. In that case, the transmission of energy may beturned off when a predetermined total amount of energy has been receivedfor consumption and storage. The transmission of energy may also beturned off when a predetermined total amount of energy has been receivedfor consumption and storage.

When electrical and/or physical parameters of the medical device and/orphysical parameters of the patient are determined, the energy may betransmitted for consumption and storage according to a transmission rateper time unit which is determined based on said parameters. The totalamount of transmitted energy may also be determined based on saidparameters.

When electrical and/or physical parameters of the medical device and/orphysical parameters of the patient are determined, the energy may besupplied from the energy storage device to the medical device forconsumption with a supply rate which is determined based on saidparameters. In that case, the total amount of energy supplied from theenergy storage device to the medical device for consumption, may bebased on said parameters.

When electrical and/or physical parameters of the medical device and/orphysical parameters of the patient are determined, a total amount ofenergy may be supplied to the medical device for consumption from theenergy storage device, where the total amount of supplied energy isdetermined based on the parameters.

When the energy received by the internal energy receiver is accumulatedand stabilized in an energy stabilizing unit, the energy balance may bedetermined based on an accumulation rate in the energy stabilizing unit,such that a storing rate in the energy storage device corresponds to anenergy reception rate in the internal energy receiver.

When a difference is detected between the total amount of energyreceived by the internal energy receiver and the total amount ofconsumed and/or stored energy, and the detected difference is related tothe integral over time of at least one measured electrical parameterrelated to said energy balance, the integral may be determined for amonitored voltage and/or current related to the energy balance.

When the derivative is determined over time of a measured electricalparameter related to the amount of consumed and/or stored energy, thederivative may be determined for a monitored voltage and/or currentrelated to the energy balance.

When using the first and second storage devices in the energy storagedevice, the second storage device may directly or indirectly supplyenergy to the medical device, wherein the change of the differencecorresponds to a change of the amount of energy accumulated in the firststorage unit. The energy balance may then be determined by detecting achange over time in the energy storing rate in the first storage device,the energy balance corresponding to the change. The change in the amountof stored energy may also be detected by determining over time thederivative of a measured electrical parameter indicating the amount ofstored energy, the derivative corresponding to the change in the amountof stored energy. A rate of change of the electrical parameter may alsobe detected, the derivative being related to the change rate. Theelectrical parameter may be a measured voltage and/or current related tothe energy balance.

The first storage device may include at least one of: a capacitor and asemiconductor, and the second storage device includes at least one of: arechargeable battery, an accumulator and a capacitor.

As mentioned above, the wireless energy may be transmitted inductivelyfrom a primary coil in the external energy source to a secondary coil inthe internal energy receiver. However, the wireless energy may also betransmitted non-inductively. For example, the wireless energy may betransmitted by means of sound or pressure variations, radio or light.The wireless energy may also be transmitted in pulses or waves and/or bymeans of an electric field.

The wireless energy may be transmitted in pulses or waves and/or bymeans of an electric field and may then be controlled by adjusting thewidth of the pulses.

When the difference between the total amount of energy received by theinternal energy receiver and the total amount of consumed energy ismeasured over time, directly or indirectly, the energy balance may bedetermined by detecting a change in the difference. In that case, thechange in the amount of consumed energy may be detected by determiningover time the derivative of a measured electrical parameter related tothe amount of consumed energy, the derivative corresponding to the rateof the change in the amount of consumed energy, wherein the rate ofchange includes the direction and speed of the change. A rate of changeof the electrical parameter may then be detected, the derivative beingrelated to the detected change rate.

When using the first and second storage devices in the energy storagedevice, the first storage device may be adapted to be charged at arelatively higher energy charging rate as compared to the second storagedevice, thereby enabling a relatively faster charging. The first storagedevice may also be adapted to be charged at multiple individual chargingoccasions more frequently as compared to the second storage device,thereby providing relatively greater life-time in terms of chargingoccasions. The first storage device may comprise at least one capacitor.Normally, only the first storage may be charged and more often thanneeded for the second storage device.

When the second storage device needs to be charged, to reduce the timeneeded for charging, the first storage device is charged at multipleindividual charging occasions, thereby leaving time in between thecharging occasions for the first storage device to charge the secondstorage device at a relatively lower energy charging rate. Whenelectrical parameters of the medical device are determined, the chargingof the second storage device may be controlled based on the parameters.A constant current or stabilizing voltage circuitry may be used forstoring energy in the second storage device.

Embodiments to Control the Wireless Energy Supply Based on the Feed BackMechanism Above

The transmission of wireless energy from the external energy source maybe controlled by applying to the external energy source electricalpulses from a first electric circuit to transmit the wireless energy,the electrical pulses having leading and trailing edges, varying thelengths of first time intervals between successive leading and trailingedges of the electrical pulses and/or the lengths of second timeintervals between successive trailing and leading edges of theelectrical pulses, and transmitting wireless energy, the transmittedenergy generated from the electrical pulses having a varied power, thevarying of the power depending on the lengths of the first and/or secondtime intervals.

Thus, wireless energy is transmitted from an external energytransmitting device placed externally to a human body to an internalenergy receiver placed internally in the human body. Electrical pulsesfrom a first electric circuit may be applied to the externaltransmitting device to transmit the wireless energy, the electricalpulses having leading and trailing edges. the lengths of first timeintervals between successive leading and trailing edges of theelectrical pulses and/or the lengths of second time intervals betweensuccessive trailing and leading edges of the electrical pulses, may bevaried. The transmitted energy generated from the electrical pulses mayfurther have a varied power, the varying of the power depending on thelengths of the first and/or second time intervals.

An apparatus adapted to transmit wireless energy from an external energytransmitting device placed externally to a human body to an internalenergy receiver placed internally in the human body, may comprise afirst electric circuit to supply electrical pulses to the externaltransmitting device, said electrical pulses having leading and trailingedges, said transmitting device adapted to supply wireless energy,wherein the electrical circuit is adapted to vary the lengths of firsttime intervals between successive leading and trailing edges of theelectrical pulses and/or the lengths of second time intervals betweensuccessive trailing and leading edges of the electrical pulses, andwherein the transmitted wireless energy, generated from the electricalpulses having a varied power, the power depending on the lengths of thefirst and/or second time intervals.

In that case, the frequency of the electrical pulses may besubstantially constant when varying the first and/or second timeintervals. When applying electrical pulses, the electrical pulses mayremain unchanged, except for varying the first and/or second timeintervals. The amplitude of the electrical pulses may be substantiallyconstant when varying the first and/or second time intervals. Further,the electrical pulses may be varied by only varying the lengths of firsttime intervals between successive leading and trailing edges of theelectrical pulses.

A train of two or more electrical pulses may be supplied in a row,wherein when applying the train of pulses, the train having a firstelectrical pulse at the start of the pulse train and having a secondelectrical pulse at the end of the pulse train, two or more pulse trainsmay be supplied in a row, wherein the lengths of the second timeintervals between successive trailing edge of the second electricalpulse in a first pulse train and leading edge of the first electricalpulse of a second pulse train are varied.

When applying the electrical pulses, the electrical pulses may have asubstantially constant current and a substantially constant voltage. Theelectrical pulses may also have a substantially constant current and asubstantially constant voltage. Further, the electrical pulses may alsohave a substantially constant frequency. The electrical pulses within apulse train may likewise have a substantially constant frequency.

When applying electrical pulses to the external energy source, theelectrical pulses may generate an electromagnetic field over theexternal energy source, the electromagnetic field being varied byvarying the first and second time intervals, and the electromagneticfield may induce electrical pulses in the internal energy receiver, theinduced pulses carrying energy transmitted to the internal energyreceiver.

The electrical pulses may be released from the first electrical circuitwith such a frequency and/or time period between leading edges of theconsecutive pulses, so that when the lengths of the first and/or secondtime intervals are varied, the resulting transmitted energy are varied.When applying the electrical pulses, the electrical pulses may have asubstantially constant frequency.

The circuit formed by the first electric circuit and the external energysource may have a first characteristic time period or first timeconstant, and when effectively varying the transmitted energy, suchfrequency time period may be in the range of the first characteristictime period or time constant or shorter.

One Embodiment of an Apparatus or Method to be Used with the FeedbackMechanism Above

The wireless energy may be used for controlling a flow of fluid and/orother bodily matter in a lumen formed by a tissue wall of a patient'sorgan. At least one portion of the tissue wall may then be gentlyconstricted to influence the flow in the lumen, and the constricted wallportion may be stimulated to cause contraction of the wall portion tofurther influence the flow in the lumen.

The object of the present embodiment is to provide an apparatus adaptedto control or a method for controlling the flow of fluids and/or otherbodily matter in lumens formed by tissue walls of bodily organs, so asto at least substantially or even completely eliminate the injuredtissue wall problems that have resulted from implanted prior art devicesthat constrict such bodily organs.

In accordance with this object of the present embodiment, there isprovided an apparatus adapted to control or a method for controlling theflow of fluids and/or other bodily matter in a lumen that is formed bythe tissue wall of a bodily organ, the apparatus comprising animplantable constriction device for gently constricting a portion of thetissue wall to influence the flow in the lumen, a stimulation device forstimulating the wall portion of the tissue wall, and a control devicefor controlling the stimulation device to stimulate the wall portion asthe constriction device constricts the wall portion to cause contractionof the wall portion to further influence the flow in the lumen.

The embodiments above may provide an advantageous combination ofconstriction and stimulation devices, which results in a two-stageinfluence on the flow of fluids and/or other bodily matter in the lumenof a bodily organ. Thus, the constriction device may gently constrictthe tissue wall by applying a relatively weak force against the wallportion, and the stimulation device may stimulate the constricted wallportion to achieve the desired final influence on the flow in the lumen.The phrase “gently constricting a portion of the tissue wall” is to beunderstood as constricting the wall portion without substantiallyhampering the blood circulation in the tissue wall.

Thus both a method for controlling the flow in the lumen and anapparatus adapted to control the flow in the lumen may be implementedaccording to different embodiments and features as follows:

Preferably, the stimulation device is adapted to stimulate differentareas of the wall portion as the constriction device constricts the wallportion, and the control device controls the stimulation device tointermittently and individually stimulate the areas of the wall portion.This intermittent and individual stimulation of different areas of thewall portion of the organ allows tissue of the wall portion to maintainsubstantially normal blood circulation during the operation of theapparatus above.

The combination of the constriction and stimulation devices enablesapplication of the apparatus or method above at any place on any kind ofbodily organs, in particular, but not limited to, tubular bodily organs,which is a significant advance in the art, as compared with priorstimulation devices that are confined to electric stimulation ofmalfunctioning sphincters.

In some applications, there will be daily adjustments of the implantedconstriction device. Therefore, the constriction device may beadjustable to enable adjustment of the constriction of the wall portionas desired, wherein the control device controls the constriction deviceto adjust the constriction of the wall portion. The control device maycontrol the constriction and stimulation devices independently of eachother, and simultaneously. Optionally, the control device may controlthe stimulation device to stimulate, or to not stimulate the wallportion while the control device controls the constriction device tochange the constriction of the wall portion.

Initially, the constriction device may be calibrated by using thecontrol device to control the stimulation device to stimulate the wallportion, while controlling the constriction device to adjust theconstriction of the wall portion until the desired restriction of theflow in the lumen is obtained.

Flow Restriction

The apparatus may be used for restricting the flow of fluids and/orother bodily matter in the lumen of a bodily organ. Thus, in oneembodiment, the constriction device is adapted to constrict the wallportion to at least restrict the flow in the lumen, and the controldevice controls the stimulation device to cause contraction of theconstricted wall portion, so that the flow in the lumen is at leastfurther restricted. Specifically, the constriction device is adapted toconstrict the wall portion to a constricted state in which the bloodcirculation in the constricted wall portion is substantiallyunrestricted and the flow in the lumen is at least restricted, and thecontrol device controls the stimulation device to cause contraction ofthe wall portion, so that the flow in the lumen is at least furtherrestricted when the wall portion is kept by the constriction device inthe constricted state.

The constriction and stimulation devices may be controlled to constrictand stimulate, respectively, to an extent that depends on the flowrestriction that is desired to be achieved in a specific application ofthe apparatus above. Thus, in accordance with a first flow restrictionoption, the control device controls the constriction device to constrictthe wall portion, such that flow in the lumen is restricted or stopped,and controls the stimulation device to stimulate the constricted wallportion to cause contraction thereof, such that flow in the lumen isfurther restricted or more safely stopped. More precisely, the controldevice may control the stimulation device in a first mode to stimulatethe constricted wall portion to further restrict or stop the flow in thelumen and to:

-   -   a) control the stimulation device in a second mode to cease the        stimulation of the wall portion to increase the flow in the        lumen; or    -   b) control the stimulation and constriction devices in the        second mode to cease the stimulation of the wall portion and        release the wall portion to restore the flow in the lumen.

Movement of Fluid and/or Other Bodily Matter in Lumen

In one embodiment the constriction device is adapted to constrict thewall portion to restrict or vary the flow in the lumen, and the controldevice controls the stimulation device to progressively stimulate theconstricted wall portion, in the downstream or upstream direction of thelumen, to cause progressive contraction of the wall portion to move thefluid and/or other bodily matter in the lumen.

Stimulation

The control device may control the stimulation device to stimulate oneor more of the areas of the wall portion at a time, for example bysequentially stimulating the different areas. Furthermore, the controldevice may control the stimulation device to cyclically propagate thestimulation of the areas along the wall portion, preferably inaccordance with a determined stimulation pattern. To achieve the desiredreaction of the tissue wall during the stimulation thereof, the controldevice may control the stimulation device to, preferably cyclically,vary the intensity of the stimulation of the wall portion.

In another embodiment, the control device controls the stimulationdevice to intermittently stimulate the areas of the wall portion withpulses that preferably form pulse trains. At least a first area and asecond area of the areas of the wall portion may be repeatedlystimulated with a first pulse train and a second pulse train,respectively, such that the first and second pulse trains over time areshifted relative to each other. For example, the first area may bestimulated with the first pulse train, while the second area is notstimulated with said second pulse train, and vice versa. Alternatively,the first and second pulse trains may be shifted relative to each other,such that the first and second pulse trains at least partially overlapeach other.

The pulse trains can be configured in many different ways. Thus, thecontrol device may control the stimulation device to vary the amplitudesof the pulses of the pulse trains, the duty cycle of the individualpulses of each pulse train, the width of each pulse of the pulse trains,the length of each pulse train, the repetition frequency of the pulsesof the pulse trains, the repetition frequency of the pulse trains, thenumber of pulses of each pulse train, and/or the off time periodsbetween the pulse trains. Several pulse trains of differentconfigurations may be employed to achieve the desired effect.

In case the control device controls the stimulation device to vary theoff time periods between pulse trains that stimulate the respective areaof the wall portion, it is also possible to control each off time periodbetween pulse trains to last long enough to restore substantially normalblood circulation in the area when the latter is not stimulated duringthe off time periods.

An electric stimulation device suitably comprises at least one,preferably a plurality of electrical elements, such as electrodes, forengaging and stimulating the wall portion with electric pulses.Optionally, the electrical elements may be placed in a fixed orientationrelative to one another. The control device controls the electricstimulation device to electrically energize the electrical elements, oneat a time, or groups of electrical elements at a time. Preferably, thecontrol device controls the electric stimulation device to cyclicallyenergize each element with electric pulses. Optionally, the controldevice may control the stimulation device to energize the electricalelements, such that the electrical elements are energized one at a timein sequence, or such that a number or groups of the electrical elementsare energized at the same time. Also, groups of electrical elements maybe sequentially energized, either randomly or in accordance with apredetermined pattern.

The electrical elements may form any pattern of electrical elements.Preferably, the electrical elements form an elongate pattern ofelectrical elements, wherein the electrical elements are applicable onthe patient's wall of the organ, such that the elongate pattern ofelectrical elements extends lengthwise along the wall of the organ, andthe elements abut the respective areas of the wall portion. The elongatepattern of electrical elements may include one or more rows ofelectrical elements extending lengthwise along the wall of the organ.Each row of electrical elements may form a straight, helical or zig-zagpath of electrical elements, or any form of path. The control device maycontrol the stimulation device to successively energize the electricalelements longitudinally along the elongate pattern of electricalelements in a direction opposite to, or in the same direction as thatof, the flow in the patient's lumen.

In accordance with one embodiment, the electrical elements form aplurality of groups of elements, wherein the groups form a series ofgroups extending along the patient's organ in the flow direction in thepatient's lumen. The electrical elements of each group of electricalelements may form a path of elements extending at least in part aroundthe patient's organ. In a first alternative, the electrical elements ofeach group of electrical elements may form more than two paths ofelements extending on different sides of the patient's organ, preferablysubstantially transverse to the flow direction in the patient's lumen.The control device may control the stimulation device to energize thegroups of electrical elements in the series of groups in random, or inaccordance with a predetermined pattern. Alternatively, the controldevice may control the stimulation device to successively energize thegroups of electrical elements in the series of groups in a directionopposite to, or in the same direction as that of, the flow in thepatient's lumen, or in both said directions starting from a positionsubstantially at the center of the constricted wall portion. Forexample, groups of energized electrical elements may form advancingwaves of energized electrical elements, as described above; that is, thecontrol device may control the stimulation device to energize the groupsof electrical elements, such that energized electrical elements form twowaves of energized electrical elements that simultaneously advance fromthe center of the constricted wall portion in two opposite directionstowards both ends of the elongate pattern of electrical elements.

Mechanical Operation

Where the operation device mechanically operates the constriction deviceof the constriction/stimulation unit, it may be non-inflatable.Furthermore, the operation device may comprise a servo system, which mayinclude a gearbox. The term “servo system” encompasses the normaldefinition of a servo mechanism, i.e., an automatic device that controlslarge amounts of power by means of very small amounts of power, but mayalternatively or additionally encompass the definition of a mechanismthat transfers a weak force acting on a moving element having a longstroke into a strong force acting on another moving element having ashort stroke. Preferably, the operation device operates the constrictiondevice in a non-magnetic and/or non-manual manner. A motor may beoperatively connected to the operation device. The operation device maybe operable to perform at least one reversible function and the motormay be capable of reversing the function.

Hydraulic Operation

Where the operation device hydraulically operates the constrictiondevice of the constriction/stimulation unit, it includes hydraulic meansfor adjusting the constriction device.

In another embodiment, the hydraulic means comprises a reservoir and anexpandable/contractible cavity in the constriction device, wherein theoperation device distributes hydraulic fluid from the reservoir toexpand the cavity, and distributes hydraulic fluid from the cavity tothe reservoir to contract the cavity. The cavity may be defined by aballoon of the constriction device that abuts the tissue wall portion ofthe patient's organ, so that the patient's wall portion is constrictedupon expansion of the cavity and released upon contraction of thecavity.

Alternatively, the cavity may be defined by a bellows that displaces arelatively large contraction element of the constriction device, forexample a large balloon that abuts the wall portion, so that thepatient's wall portion is constricted upon contraction of the bellowsand released upon expansion of the bellows. Thus, a relatively smalladdition of hydraulic fluid to the bellows causes a relatively largeincrease in the constriction of the wall portion. Such a bellows mayalso be replaced by a suitably designed piston/cylinder mechanism.

Where the hydraulic means comprises a cavity in the constriction device,the apparatus above can be designed in accordance with the optionslisted below.

1) The reservoir comprises first and second wall portions, and theoperation device displaces the first and second wall portions relativeto each other to change the volume of the reservoir, such that fluid isdistributed from the reservoir to the cavity, or from the cavity to thereservoir.

-   -   1a) The first and second wall portions of the reservoir are        displaceable relative to each other by at least one of a        magnetic device, a hydraulic device or an electric control        device.

means.

2) The apparatus comprises a fluid conduit between the reservoir and thecavity, wherein the reservoir forms part of the conduit. The conduit andreservoir and apparatus are devoid of any non-return valve. Thereservoir forms a fluid chamber with a variable volume, and distributesfluid from the chamber to the cavity by a reduction in the volume of thechamber and withdraws fluid from the cavity by an expansion of thevolume of the chamber. The apparatus further comprises a motor fordriving the reservoir, comprising a movable wall of the reservoir forchanging the volume of the chamber.

In another embodiment, the operation device comprises a reverse servooperatively connected to the hydraulic means. The term “reverse servo”is to be understood as a mechanism that transfers a strong force actingon a moving element having a short stroke into a weak force acting onanother moving element having a long stroke; i.e., the reverse functionof a normal servo mechanism. Thus, minor changes in the amount of fluidin a smaller reservoir could be transferred by the reverse servo intomajor changes in the amount of fluid in a larger reservoir. The reverseservo is particularly suited for manual operation thereof.

Design of Control Device

The control device suitably controls the constriction/stimulation unitfrom outside the patient's body. Preferably, the control device isoperable by the patient. For example, the control device may comprise amanually operable switch for switching on and off theconstriction/stimulation unit, wherein the switch is adapted forsubcutaneous implantation in the patient to be manually or magneticallyoperated from outside the patient's body. Alternatively, the controldevice may comprise a hand-held wireless remote control, which isconveniently operable by the patient to switch on and off theconstriction/stimulation unit. The wireless remote control may also bedesigned for application on the patient's body like a wristwatch. Such awristwatch type of remote control may emit a control signal or the likethat follows the patient's body to implanted signal responsive means ofthe apparatus.

The transmission of wireless energy from the external energytransmitting device may be controlled by applying to the external energytransmitting device electrical pulses from a first electric circuit totransmit the wireless energy, the electrical pulses having leading andtrailing edges, varying the lengths of first time intervals betweensuccessive leading and trailing edges of the electrical pulses and/orthe lengths of second time intervals between successive trailing andleading edges of the electrical pulses, and transmitting wirelessenergy, the transmitted energy generated from the electrical pulseshaving a varied power, the varying of the power depending on the lengthsof the first and/or second time intervals.

Thus is provided a method of controlling transmission of wirelessenergy, and the method may further comprise:

applying to the external transmitting device electrical pulses from afirst electric circuit to transmit the wireless energy, the electricalpulses having leading and trailing edges,

varying the lengths of first time intervals between successive leadingand trailing edges of the electrical pulses and/or the lengths of secondtime intervals between successive trailing and leading edges of theelectrical pulses, and

transmitting wireless energy, the transmitted energy generated from theelectrical pulses having a varied power, the varying of the powerdepending on the lengths of the first and/or second time intervals.

Also is provided an apparatus adapted to transmit wireless energy froman external energy transmitting device placed externally to a human bodyto an internal energy receiver placed internally in the human body. Theapparatus may comprise,

a first electric circuit to supply electrical pulses to the externaltransmitting device, said electrical pulses having leading and trailingedges, said transmitting device adapted to supply wireless energy,wherein

the electrical circuit being adapted to vary the lengths of first timeintervals between successive leading and trailing edges of theelectrical pulses and/or the lengths of second time intervals betweensuccessive trailing and leading edges of the electrical pulses, andwherein

the transmitted wireless energy, generated from the electrical pulseshaving a varied power, the power depending on the lengths of the firstand/or second time intervals.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in more detail and withreference to the accompanying drawings, in which:

FIG. 1 is a schematic block diagram illustrating an arrangement forsupplying an accurate amount of energy to an electrically operablemedical device.

FIG. 2 is a more detailed block diagram of an apparatus for controllingtransmission of wireless energy supplied to an electrically operablemedical device implanted in a patient.

FIG. 3 is a schematic circuit diagram illustrating a proposed design ofan apparatus for controlling transmission of wireless energy, accordingto a possible implementation example.

FIGS. 4-12 are diagrams illustrating various measurements obtained whenimplementing the inventive method and apparatus according to the circuitdiagram of FIG. 3.

FIGS. 13a-13e schematically illustrate different states of operation ofone embodiment of the apparatus.

FIGS. 13f-3h illustrate different states of operation of a modificationof the above embodiment.

FIGS. 13i-13k illustrate an alternative mode of operation of themodification of the above embodiment.

FIG. 14 is a longitudinal cross-section of one embodiment of theapparatus including a constriction device and an electric stimulationdevice.

FIG. 15 is a cross-section along line III-III in FIG. 10.

FIG. 16 is the same cross-section shown in FIG. 11, but with theapparatus in a different state of operation.

FIG. 17a is a diagram showing an example of pulses to be modified.

FIG. 17b is a diagram showing an example of a pulse train to bemodified.

DETAILED DESCRIPTION

Briefly described, wireless energy is transmitted by means of a primarycoil in an external energy source located outside a mammal patient andis received inductively by means of a secondary coil in an internalenergy receiver located inside the patient. The internal energy receiveris connected to an electrically operable medical device implanted in thepatient, for directly or indirectly supplying received energy to themedical device. Feedback control information is transferred from thesecondary coil to the primary coil by switching the secondary coil onand off to induce a detectable impedance load variation in the primarycoil encoding the feedback control information. The feedback controlinformation relates to the energy for operating the medical device andis used for controlling the transmission of wireless energy from theexternal energy source

An energy balance may be determined between the energy received by theinternal energy receiver and the energy used for the medical device, andthe transmission of wireless energy is then controlled based on thedetermined energy balance and in response to the feedback controlinformation. The energy balance thus provides an accurate indication ofthe correct amount of energy needed, which is sufficient to operate themedical device properly, but without causing undue temperature rise.

In FIG. 1, an arrangement is schematically illustrated for supplying anaccurate amount of energy to an electrically operable medical device 100implanted in a patient, whose skin is indicated by a vertical line Sseparating the interior “Int” of the patient from the exterior “Ext”.The medical device 100 is connected to an internal energy receiver 102,likewise located inside the patient, preferably just beneath the skin S.Generally speaking, the energy receiver 102 may be placed in theabdomen, thorax, muscle fascia (e.g. in the abdominal wall),subcutaneously, or at any other suitable location. The energy receiver102 is adapted to receive wireless energy E transmitted from an externalenergy source 104 located outside the skin S in the vicinity of theenergy receiver 102.

The wireless energy E is transferred by means of a primary coil arrangedin the energy source 104 and an adjacent secondary coil arranged in theenergy receiver 102. When an electric current is fed through the primarycoil, energy in the form of a voltage is induced in the secondary coilwhich can be used to operate the medical device 100, e.g. after storingthe incoming energy in an energy storing device or accumulator, such asa battery or a capacitor, not shown in this figure.

The internal energy receiver 102 is adapted to transfer suitablefeedback control information FB from the secondary coil to the primarycoil by switching the secondary coil on and off to induce a detectableimpedance load variation in the primary coil. This load variation iscreated and controlled to encode the feedback control information in auseful manner. The feedback control information thus communicated fromthe energy receiver 102 over to the energy source 104, generally relatesto the energy for operating the medical device 100. The feedback controlinformation is then used for controlling the transmission of wirelessenergy from the external energy source 104. The amount of transferredenergy is regulated by means of an external control unit 106 controllingthe energy source 104.

An internal control unit 108 may be implanted in the patient connectedto the medical device 100. The internal control unit 108 is used tocontrol the on and off switching of the secondary coil. The feedbackcontrol information FB may include at least one predetermined parameterrelating to the received energy. The predetermined parameter may furtherbe variable. When using the internal control unit 108, the feedbackcontrol information may relate to the received energy and may alsorequire artificial intelligence to be generated.

The on and off switching of the secondary coil may be executed by meansof an implantable switch 110 (SW) at the energy receiver 102, and theswitch 110 is connected to and controlled by the internal control unit108. The switch may be an electronic switch such as a transistor.Further, the internal control unit 108 may comprise a memory 108 a forstoring the transferred feedback control information FB.

The energy balance mentioned above may be determined by means of theinternal control unit 108, and the feedback control information willthen relate to the determined energy balance. In that case, the externalcontrol unit. 106 may be used to control the transmission of wirelessenergy E from the external energy source 104 based on the determinedenergy balance and using the received feedback control information FB.

Alternatively, the external control unit 106 may be used to determinethe energy balance above, based on the feedback control information FBwhich in that case comprises measurements relating to characteristics ofthe medical device. The external control unit 106 is then further usedto control the transmission of wireless energy from the external energysource 104 based on the determined energy balance and using the receivedfeedback control information FB.

The internal control unit 108 may be arranged to receive variousmeasurements obtained by suitable sensors or the like, not shown,measuring certain characteristics of the medical device 100, somehowreflecting the energy needed for proper operation of the medical device100. Moreover, the current condition of the patient may also be detectedby means of suitable measuring devices or sensors, in order to provideparameters reflecting the patient's condition. Hence, suchcharacteristics and/or parameters may be related to the current state ofthe medical device 100, such as power consumption, operational mode andtemperature, as well as the patient's condition reflected by, e.g., bodytemperature, blood pressure, heartbeats and breathing.

Furthermore, an energy storing device or accumulator, not shown here,may also be connected to the energy receiver 102 for accumulatingreceived energy for later use by the medical device 100. Alternativelyor additionally, characteristics of such an energy storing device, alsorelating to the energy, may be measured as well. The energy storingdevice may be a battery, and the measured characteristics may be relatedto the current state of the battery, such as voltage, temperature, etc.In order to provide sufficient voltage and current to the medical device100, and also to avoid excessive heating, it is clearly understood thatthe battery should be charged optimally by receiving a correct amount ofenergy from the energy receiver 102, i.e. not too little or too much.The energy storing device may also be a capacitor with correspondingcharacteristics.

For example, battery characteristics may be measured on a regular basisto determine the current state of the battery, which then may be storedas state information in a suitable storage means in the internal controlunit 108. Thus, whenever new measurements are made, the stored batterystate information can be updated accordingly. In this way, the state ofthe battery can be “calibrated” by transferring a correct amount ofenergy, so as to maintain the battery in an optimal condition.

Thus, the internal control unit 108 may be adapted to determine theenergy balance and/or the currently required amount of energy, (eitherenergy per time unit or accumulated energy) based on measurements madeby the above-mentioned sensors or measuring devices on the medicaldevice 100, or the patient, or an energy storing device if used, or anycombination thereof. The amount of energy transmitted from the energysource 104 may then be regulated in response to the received feedbackcontrol information.

Alternatively, sensor measurements can be transmitted to the externalcontrol unit 106 wherein the energy balance and/or the currentlyrequired amount of energy can be determined by the external control unit106, thus basically integrating the above-described function of theinternal control unit 108 in the external control unit 106. In thatcase, the internal control unit 108 can be omitted and the sensormeasurements are comprised in the feedback control information FB. Theenergy balance and the currently required amount of energy can then bedetermined by the external control unit 106 based on those sensormeasurements.

Hence, the present solution employs the feed back of informationindicating the required energy, which is more efficient than previoussolutions because it is based on the actual use of energy that iscompared to the received energy, e.g. with respect to the amount ofenergy, the energy difference, or the energy receiving rate as comparedto the energy rate used by the medical device. The medical device mayuse the received energy either for consuming or for storing the energyin an energy storage device or the like. The different parametersdiscussed above would thus be used if relevant and needed and then as atool for determining the actual energy balance. However, such parametersmay also be needed per se for any actions taken internally tospecifically operate the medical device.

The feedback control information FB may further be modulated withrespect to frequency, phase or amplitude.

To conclude, the energy supply arrangement illustrated in FIG. 1 mayoperate basically in the following manner, in the case when thetransmission of wireless energy is controlled based on the energybalance described above. The energy balance may first be determined bythe internal control unit 108. Feedback control information FB relatingto the energy is also created by the internal control unit 108, and thefeedback control information FB is transmitted from the energy receiver102 to the energy source 104. Alternatively, the energy balance can bedetermined by the external control unit 106 instead depending on theimplementation, as mentioned above. In that case, the feedback controlinformation FB may carry measurement results from various sensors. Theamount of energy emitted from the energy source 104 can then beregulated by the external control unit 106, based on the determinedenergy balance, e.g. in response to the received feedback controlinformation FB. This process may be repeated intermittently at certainintervals during ongoing energy transfer, or may be executed on a moreor less continuous basis during the energy transfer.

The amount of transferred energy can generally be regulated by adjustingvarious transmission parameters in the energy source 104, such asvoltage, current, amplitude, wave frequency and pulse characteristics.

FIG. 2 illustrates different embodiments for how received energy can besupplied to and used by a medical device 200. Similar to the example ofFIG. 1, an internal energy receiver 202 receives wireless energy E froman external energy source 204 which is controlled by a transmissioncontrol unit 206. The internal energy receiver 202 may comprise aconstant voltage circuit, indicated as a dashed box “constant V” in thefigure, for supplying energy at constant voltage to the medical device200. The internal energy receiver 202 may further comprise a constantcurrent circuit, indicated as a dashed box “constant C” in the figure,for supplying energy at constant current to the medical device 200.

The medical device 200 comprises an energy consuming part 200 a whichmay be a motor, pump, restriction device, or any other medical appliancethat requires energy for its electrical operation. The medical device200 may further comprise an energy storage device 200 b for storingenergy supplied from the internal energy receiver 202. Thus, thesupplied energy may be directly consumed by the energy consuming part200 a or stored by the energy storage device 200 b, or the suppliedenergy may be partly consumed and partly stored. The medical device 200may further comprise an energy stabilizing unit 200 c for stabilizingthe energy supplied from the internal energy receiver 202. Thus, theenergy may be supplied in a fluctuating manner such that it may benecessary to stabilize the energy before consumed or stored.

The energy supplied from the internal energy receiver 202 may further beaccumulated and/or stabilized by a separate energy stabilizing unit 208located outside the medical device 200, before being consumed and/orstored by the medical device 200. Alternatively, the energy stabilizingunit 208 may be integrated in the internal energy receiver 202. Ineither case, the energy stabilizing unit 208 may comprise a constantvoltage circuit and/or a constant current circuit.

It should be noted that FIG. 1 and FIG. 2 illustrate some possible butnon-limiting implementation options regarding how the various shownfunctional components and elements can be arranged and connected to eachother. However, the skilled person will readily appreciate that manyvariations and modifications can be made within the scope of the presentinvention.

A method is thus provided for controlling transmission of wirelessenergy supplied to an electrically operable medical device implanted ina patient. The wireless energy is transmitted from an external energysource located outside the patient and is received by an internal energyreceiver located inside the patient, the internal energy receiver beingconnected to the medical device for directly or indirectly supplyingreceived energy thereto. An energy balance is determined between theenergy received by the internal energy receiver and the energy used forthe medical device. the transmission of wireless energy from theexternal energy source is then controlled based on the determined energybalance.

An apparatus is also provided for controlling transmission of wirelessenergy supplied to an electrically operable medical device implanted ina patient. The apparatus is adapted to transmit the wireless energy froman external energy source located outside the patient which is receivedby an internal energy receiver located inside the patient, the internalenergy receiver being connected to the medical device for directly orindirectly supplying received energy thereto. The apparatus may furtherbe adapted to determine an energy balance between the energy received bythe internal energy receiver and the energy used for the medical device,and control the transmission of wireless energy from the external energysource, based on the determined energy balance.

A change in the energy balance may be detected to control thetransmission of wireless energy based on the detected energy balancechange. A difference may also be detected between energy received by theinternal energy receiver and energy used for the medical device, tocontrol the transmission of wireless energy based on the detected energydifference.

When controlling the energy transmission, the amount of transmittedwireless energy may be decreased if the detected energy balance changeimplies that the energy balance is increasing, or vice versa. Thedecrease/increase of energy transmission may further correspond to adetected change rate.

The amount of transmitted wireless energy may further be decreased ifthe detected energy difference implies that the received energy isgreater than the used energy, or vice versa. The decrease/increase ofenergy transmission may then correspond to the magnitude of the detectedenergy difference.

As mentioned above, the energy used for the medical device may beconsumed to operate the medical device, and/or stored in at least oneenergy storage device of the medical device.

In one alternative, substantially all energy used for the medical deviceis consumed (e.g. by the consuming part 200 a of FIG. 2) to operate themedical device. In that case, the energy may be consumed after beingstabilized in at least one energy stabilizing unit of the medicaldevice.

In another alternative, substantially all energy used for the medicaldevice is stored in the at least one energy storage device. In yetanother alternative, the energy used for the medical device is partlyconsumed to operate the medical device and partly stored in the at leastone energy storage device.

The energy received by the internal energy receiver may be stabilized bya capacitor, before the energy is supplied directly or indirectly to themedical device.

The difference between the total amount of energy received by theinternal energy receiver and the total amount of consumed and/or storedenergy may be directly or indirectly measured over time, and the energybalance can then be determined based on a detected change in the totalamount difference.

The energy received by the internal energy receiver may further beaccumulated and stabilized in an energy stabilizing unit, before theenergy is supplied to the medical device. In that case, the energybalance may be determined based on a detected change followed over timein the amount of consumed and/or stored energy. Further, the change inthe amount of consumed and/or stored energy may be detected bydetermining over time the derivative of a measured electrical parameterrelated to the amount of consumed and/or stored energy, where thederivative at a first given moment is corresponding to the rate of thechange at the first given moment, wherein the rate of change includesthe direction and speed of the change. The derivative may further bedetermined based on a detected rate of change of the electricalparameter.

The energy received by the internal energy receiver may be supplied tothe medical device with at least one constant voltage, wherein theconstant voltage is created by a constant voltage circuitry. In thatcase, the energy may be supplied with at least two different voltages,including the at least one constant voltage.

The energy received by the internal energy receiver may also be suppliedto the medical device with at least one constant current, wherein theconstant current is created by a constant current circuitry. In thatcase, the energy may be supplied with at least two different currentsincluding the at least one constant current.

The energy balance may also be determined based on a detected differencebetween the total amount of energy received by the internal energyreceiver and the total amount of consumed and/or stored energy, thedetected difference being related to the integral over time of at leastone measured electrical parameter related to the energy balance. In thatcase, values of the electrical parameter may be plotted over time as agraph in a parameter-time diagram, and the integral can be determinedfrom the size of the area beneath the plotted graph. The integral of theelectrical parameter may relate to the energy balance as an accumulateddifference between the total amount of energy received by the internalenergy receiver and the total amount of consumed and/or stored energy.

The energy storage device in the medical device may include at least oneof: a rechargeable battery, an accumulator or a capacitor. The energystabilizing unit may include at least one of: an accumulator, acapacitor or a semiconductor adapted to stabilize the received energy.

When the energy received by the internal energy receiver is accumulatedand stabilized in an energy stabilizing unit before energy is suppliedto the medical device and/or energy storage device, the energy may besupplied to the medical device and/or energy storage device with atleast one constant voltage, as maintained by a constant voltagecircuitry. In that case, the medical device and energy storage devicemay be supplied with at least two different voltages, wherein at leastone voltage is constant, maintained by the constant voltage circuitry.

Alternatively, when the energy received by the internal energy receiveris accumulated and stabilized in an energy stabilizing unit beforeenergy is supplied to the medical device and/or energy storage device,the energy may be supplied to the medical device and/or energy storagedevice with at least one constant current, as maintained by a constantcurrent circuitry. In that case, the medical device and energy storagedevice may be supplied with at least two different currents wherein atleast one current is constant, maintained by the constant currentcircuitry.

The wireless energy may be initially transmitted according to apredetermined energy consumption plus storage rate. In that case, thetransmission of wireless energy may be turned off when a predeterminedtotal amount of energy has been transmitted. The energy received by theinternal energy receiver may then also be accumulated and stabilized inan energy stabilizing unit before being consumed to operate the medicaldevice and/or stored in the energy storage device until a predeterminedtotal amount of energy has been consumed and/or stored.

Further, the wireless energy may be first transmitted with thepredetermined energy rate, and then transmitted based on the energybalance which can be determined by detecting the total amount ofaccumulated energy in the energy stabilizing unit. Alternatively, theenergy balance can be determined by detecting a change in the currentamount of accumulated energy in the energy stabilizing unit. In yetanother alternative, the energy balance, can be determined by detectingthe direction and rate of change in the current amount of accumulatedenergy in the energy stabilizing unit.

The transmission of wireless energy may be controlled such that anenergy reception rate in the internal energy receiver corresponds to theenergy consumption and/or storage rate. In that case, the transmissionof wireless energy may be turned off when a predetermined total amountof energy has been consumed.

The energy received by the internal energy receiver may be firstaccumulated and stabilized in an energy stabilizing unit, and thenconsumed or stored by the medical device until a predetermined totalamount of energy has been consumed. In that case, the energy balance maybe determined based on a detected total amount of accumulated energy inthe energy stabilizing unit. Alternatively, the energy balance may bedetermined by detecting a change in the current amount of accumulatedenergy in the energy stabilizing unit. In yet another alternative, theenergy balance may be determined by detecting the direction and rate ofchange in the current amount of accumulated energy in the energystabilizing unit.

As mentioned in connection with FIG. 1, suitable sensors may be used formeasuring certain characteristics of the medical device and/or detectingthe current condition of the patient, somehow relating to the energyneeded for proper operation of the medical device. Thus, electricaland/or physical parameters of the medical device and/or physicalparameters of the patient may be determined, and the energy can then betransmitted with a transmission rate which is determined based on theparameters. Further, the transmission of wireless energy may becontrolled such that the total amount of transmitted energy is based onsaid parameters.

The energy received by the internal energy receiver may be firstaccumulated and stabilized in an energy stabilizing unit, and thenconsumed until a predetermined total amount of energy has been consumed.The transmission of wireless energy may further be controlled such thatan energy reception rate at the internal energy receiver corresponds toa predetermined energy consumption rate.

Further, electrical and/or physical parameters of the medical deviceand/or physical parameters of the patient may be determined, in order todetermine the total amount of transmitted energy based on theparameters. In that case, the energy received by the internal energyreceiver may be first accumulated and stabilized in an energystabilizing unit, and then consumed until a predetermined total amountof energy has been consumed.

The energy is stored in the energy storage device according to apredetermined storing rate. The transmission of wireless energy may thenbe turned off when a predetermined total amount of energy has beenstored. The transmission of wireless energy can be further controlledsuch that an energy reception rate at the internal energy receivercorresponds to the predetermined storing rate.

The energy storage device of the medical device may comprise a firststorage device and a second storage device, wherein the energy receivedby the internal energy receiver is first stored in the first storagedevice, and the energy is then supplied from the first storage device tothe second storage device at a later stage.

When using the first and second storage devices in the energy storagedevice, the energy balance may be determined in different ways. Firstly,the energy balance may be determined by detecting the current amount ofenergy stored in the first storage device, and the transmission ofwireless energy may then be controlled such that a storing rate in thesecond storage device corresponds to an energy reception rate in theinternal energy receiver. Secondly, the energy balance may be determinedbased on a detected total amount of stored energy in the first storagedevice. Thirdly, the energy balance may be determined by detecting achange in the current amount of stored energy in the first storagedevice. Fourthly, the energy balance may be determined by detecting thedirection and rate of change in the current amount of stored energy inthe first storage device.

Stabilized energy may be first supplied from the first storage device tothe second storage device with a constant current, as maintained by aconstant current circuitry, until a measured voltage over the secondstorage device reaches a predetermined maximum voltage, and thereaftersupplied from the first storage device to the second storage energystorage device with a constant voltage, as maintained by a constantvoltage circuitry. In that case, the transmission of wireless energy maybe turned off when a predetermined minimum rate of transmitted energyhas been reached.

The transmission of energy may further be controlled such that theamount of energy received by the internal energy receiver corresponds tothe amount of energy stored in the second storage device. In that case,the transmission of energy may be controlled such that an energyreception rate at the internal energy receiver corresponds to an energystoring rate in the second storage device. The transmission of energymay also be controlled such that a total amount of received energy atthe internal energy receiver corresponds to a total amount of storedenergy in the second storage device.

In the case when the transmission of wireless energy is turned off whena predetermined total amount of energy has been stored, electricaland/or physical parameters of the medical device and/or physicalparameters of the patient may be determined during a first energystoring procedure, and the predetermined total amount of energy may bestored in a subsequent energy storing procedure based on the parameters.

When electrical and/or physical parameters of the medical device and/orphysical parameters of the patient are determined, the energy may bestored in the energy storage device with a storing rate which isdetermined based on the parameters. In that case, a total amount ofenergy may be stored in the energy storage device, the total amount ofenergy being determined based on the parameters. The transmission ofwireless energy may then be automatically turned off when the totalamount of energy has been stored. The transmission of wireless energymay further be controlled such that an energy reception rate at theinternal energy receiver corresponds to the storing rate.

When electrical and/or physical parameters of the medical device and/orphysical parameters of the patient are determined, a total amount ofenergy may be stored in the energy storage device, the total amount ofenergy being determined based on said parameters. The transmission ofenergy may then be controlled such that the total amount of receivedenergy at the internal energy receiver corresponds to the total amountof stored energy. Further, the transmission of wireless energy may beautomatically turned off when the total amount of energy has beenstored.

When the energy used for the medical device is partly consumed andpartly stored, the transmission of wireless energy may be controlledbased on a predetermined energy consumption rate and a predeterminedenergy storing rate. In that case, the transmission of energy may beturned off when a predetermined total amount of energy has been receivedfor consumption and storage. The transmission of energy may also beturned off when a predetermined total amount of energy has been receivedfor consumption and storage.

When electrical and/or physical parameters of the medical device and/orphysical parameters of the patient are determined, the energy may betransmitted for consumption and storage according to a transmission rateper time unit which is determined based on said parameters. The totalamount of transmitted energy may also be determined based on saidparameters.

When electrical and/or physical parameters of the medical device and/orphysical parameters of the patient are determined, the energy may besupplied from the energy storage device to the medical device forconsumption with a supply rate which is determined based on saidparameters. In that case, the total amount of energy supplied from theenergy storage device to the medical device for consumption, may bebased on said parameters.

When electrical and/or physical parameters of the medical device and/orphysical parameters of the patient are determined, a total amount ofenergy may be supplied to the medical device for consumption from theenergy storage device, where the total amount of supplied energy isdetermined based on the parameters.

When the energy received by the internal energy receiver is accumulatedand stabilized in an energy stabilizing unit, the energy balance may bedetermined based on an accumulation rate in the energy stabilizing unit,such that a storing rate in the energy storage device corresponds to anenergy reception rate in the internal energy receiver.

When a difference is detected between the total amount of energyreceived by the internal energy receiver and the total amount ofconsumed and/or stored energy, and the detected difference is related tothe integral over time of at least one measured electrical parameterrelated to said energy balance, the integral may be determined for amonitored voltage and/or current related to the energy balance.

When the derivative is determined over time of a measured electricalparameter related to the amount of consumed and/or stored energy, thederivative may be determined for a monitored voltage and/or currentrelated to the energy balance.

When using the first and second storage devices in the energy storagedevice, the second storage device may directly or indirectly supplyenergy to the medical device, wherein the change of the differencecorresponds to a change of the amount of energy accumulated in the firststorage unit. The energy balance may then be determined by detecting achange over time in the energy storing rate in the first storage device,the energy balance corresponding to the change. The change in the amountof stored energy may also be detected by determining over time thederivative of a measured electrical parameter indicating the amount ofstored energy, the derivative corresponding to the change in the amountof stored energy. A rate of change of the electrical parameter may alsobe detected, the derivative being related to the change rate. Theelectrical parameter may be a measured voltage and/or current related tothe energy balance.

The first storage device may include at least one of: a capacitor and asemiconductor, and the second storage device includes at least one of: arechargeable battery, an accumulator and a capacitor.

As mentioned above, the wireless energy may be transmitted inductivelyfrom a primary coil in the external energy source to a secondary coil inthe internal energy receiver. However, the wireless energy may also betransmitted non-inductively. For example, the wireless energy may betransmitted by means of sound or pressure variations, radio or light.The wireless energy may also be transmitted in pulses or waves and/or bymeans of an electric field.

The wireless energy may also be transmitted in pulses or waves and/or bymeans of an electric field. The transmission of wireless energy may becontrolled by adjusting the width of the pulses.

When the difference between the total amount of energy received by theinternal energy receiver and the total amount of consumed energy ismeasured over time, directly or indirectly, the energy balance may bedetermined by detecting a change in the difference. In that case, thechange in the amount of consumed energy may be detected by determiningover time the derivative of a measured electrical parameter related tothe amount of consumed energy, the derivative corresponding to the rateof the change in the amount of consumed energy, wherein the rate ofchange includes the direction and speed of the change. A rate of changeof the electrical parameter may then be detected, the derivative beingrelated to the detected change rate.

When using the first and second storage devices in the energy storagedevice, the first storage device may be adapted to be charged at arelatively higher energy charging rate as compared to the second storagedevice, thereby enabling a relatively faster charging. The first storagedevice may also be adapted to be charged at multiple individual chargingoccasions more frequently as compared to the second storage device,thereby providing relatively greater life-time in terms of chargingoccasions. The first storage device may comprise at least one capacitor.Normally, only the first storage may be charged and more often thanneeded for the second storage device.

When the second storage device needs to be charged, to reduce the timeneeded for charging, the first storage device is charged at multipleindividual charging occasions, thereby leaving time in between thecharging occasions for the first storage device to charge the secondstorage device at a relatively lower energy charging rate. Whenelectrical parameters of the medical device are determined, the chargingof the second storage device may be controlled based on the parameters.A constant current or stabilizing voltage circuitry may be used forstoring energy in the second storage device.

The transmission of wireless energy from the external energy source maybe controlled by applying to the external energy source electricalpulses from a first electric circuit to transmit the wireless energy,the electrical pulses having leading and trailing edges, varying thelengths of first time intervals between successive leading and trailingedges of the electrical pulses and/or the lengths of second timeintervals between successive trailing and leading edges of theelectrical pulses, and transmitting wireless energy, the transmittedenergy generated from the electrical pulses having a varied power, thevarying of the power depending on the lengths of the first and/or secondtime intervals.

In that case, the frequency of the electrical pulses may besubstantially constant when varying the first and/or second timeintervals. When applying electrical pulses, the electrical pulses mayremain unchanged, except for varying the first and/or second timeintervals. The amplitude of the electrical pulses may be substantiallyconstant when varying the first and/or second time intervals. Further,the electrical pulses may be varied by only varying the lengths of firsttime intervals between successive leading and trailing edges of theelectrical pulses.

A train of two or more electrical pulses may be supplied in a row,wherein when applying the train of pulses, the train having a firstelectrical pulse at the start of the pulse train and having a secondelectrical pulse at the end of the pulse train, two or more pulse trainsmay be supplied in a row, wherein the lengths of the second timeintervals between successive trailing edge of the second electricalpulse in a first pulse train and leading edge of the first electricalpulse of a second pulse train are varied.

When applying the electrical pulses, the electrical pulses may have asubstantially constant current and a substantially constant voltage. Theelectrical pulses may also have a substantially constant current and asubstantially constant voltage. Further, the electrical pulses may alsohave a substantially constant frequency. The electrical pulses within apulse train may likewise have a substantially constant frequency.

When applying electrical pulses to the external energy source, theelectrical pulses may generate an electromagnetic field over theexternal energy source, the electromagnetic field being varied byvarying the first and second time intervals, and the electromagneticfield may induce electrical pulses in the internal energy receiver, theinduced pulses carrying energy transmitted to the internal energyreceiver.

The electrical pulses may be released from the first electrical circuitwith such a frequency and/or time period between leading edges of theconsecutive pulses, so that when the lengths of the first and/or secondtime intervals are varied, the resulting transmitted energy are varied.When applying the electrical pulses, the electrical pulses may have asubstantially constant frequency.

The circuit formed by the first electric circuit and the external energysource may have a first characteristic time period or first timeconstant, and when effectively varying the transmitted energy, suchfrequency time period may be in the range of the first characteristictime period or time constant or shorter.

The feedback signal may be related to the amount of energy beingreceived in the internal energy receiver. The external energy source maythen further comprise an electronic circuit for comparing the feedbacksignal with the amount of energy transmitted by the external energysource. The electronic circuit may comprise an analyzer adapted toanalyze the amount of energy being transmitted and adapted to receivethe feedback signal related to the amount of energy received in thereceiver, and further adapted to determine the special energy balance bycomparing the amount of transmitted energy and the feedback signalrelated to the amount of received information. The external energysource may be adapted to use the feedback signal to adjust the level ofthe transmitted energy.

The external energy source may be adapted to transfer data related tothe amount of transmitted energy to the receiver, and wherein thefeedback signal is related to the amount of energy received in thereceiver the receiver compared to the amount of the transmitted energy.The external energy source may also be adapted to use the feedbacksignal to adjust the level of the transmitted energy.

When the energy is transferred inductively, the feedback signal may berelated to a coupling factor between the primary coil and the secondarycoil. The external energy source may then be adapted to increase theamount of transferred energy to the internal energy receiver until apredetermined response of the coupling factor is detected. The externalenergy source may further comprise an indicator adapted to indicate alevel of the coupling factor. The external energy source may furthercomprise an indicator adapted to indicate an optimal placement of thesecondary coil in relation to the primary coil to optimize the couplingfactor.

While the invention has been described with reference to specificexemplary embodiments, the description is in general only intended toillustrate the inventive concept and should not be taken as limiting thescope of the invention. In particular, the skilled person will readilyunderstand that the above-described embodiments and examples can beimplemented both as a method and an apparatus. The present invention andvarious possible embodiments are generally defined by the followingclaims.

DESCRIPTION OF POSSIBLE IMPLEMENTATION EXAMPLES

The schematic FIG. 3 shows a circuit diagram of one of the proposeddesigns of the invented apparatus for controlling transmission ofwireless energy, or energy balance control system. The schematic showsthe energy balance measuring circuit that has an output signal centeredon 2.5V and that is proportional to the energy imbalance. A signal levelat 2.5V means that energy balance exists, if the level drops below 2.5Venergy is drawn from the power source in the implant and if the levelrises above 2.5V energy is charged into the power source. The outputsignal from the circuit is typically feed to an A/D converter andconverted into a digital format. The digital information can then besent to the external transmitter allowing it to adjust the level of thetransmitted power. Another possibility is to have a completely analogsystem that uses comparators comparing the energy balance level withcertain maximum and minimum thresholds sending information to anexternal transmitter if the balance drifts out of the max/min window.

The schematic FIG. 3 shows a circuit implementation for a system thattransfers power to the implant from outside of the body using inductiveenergy transfer. An inductive energy transfer system typically uses anexternal transmitting coil and an internal receiving coil. The receivingcoil, L1, is included in the schematic FIG. 3; the transmitting parts ofthe system are excluded.

The implementation of the general concept of energy balance and the waythe information is transmitted to the external energy transmitter can ofcourse be implemented in numerous different ways. The schematic FIG. 3and the above described method of evaluating and transmitting theinformation should only be regarded as examples of how to implement thecontrol system.

Circuit Details

In the schematic FIG. 3 the symbols Y1, Y2, Y3 and so on symbolize testpoints within the circuit. References to the test points are found onthe graphs in the diagrams following later in the text. The componentsin the diagram and their respective values are values that work in thisparticular implementation which of course is only one of an infinitenumber of possible design solutions.

Energy to power the circuit is received by the energy receiving coil L1.Energy to the implant is transmitted in this particular case at afrequency of 25 kHz. The energy balance output signal is present at testpoint Y1.

The diagram in FIG. 4 shows the voltage, Y7 x, over the receiving coilL1 and the input power, Y9, received by the coil from the externaltransmitter. The power graph, Y9, is normalized and varies between 0-1where 1 signifies maximum power and 0 no power; hence Y9 does not showthe absolute value of the received power level. The power test point Y9is not present in the schematic, it is an amplitude modulation signal onthe transmitter signal power. In the diagram it can be seen that the Y7x voltage over the receiving coil L1 increases as the power from theexternal transmitter increases. When the Y7 x voltage reaches the levelwhere actual charging of the power source, C1, in the implant commencesthe Y7 x level increases at a much slower rate as the input power isincreased because of the load that the power source impart on thereceiving coil.

The receiving coil L1 is connected to a rectifying bridge with fourSchottky diodes, D1 x-D4 x. The output voltage from the bridge, Y7, isshown in the diagram of FIG. 5. The capacitor C6 absorbs the highfrequency charging currents from the bridge and together with theSchottky diode D3 prevents the 25 kHz energy transmission frequency fromentering into the rest of the circuit. This is beneficial since theenergy balance of the system is measured as the voltage across R1, whichwith out the C6-D3 combination would contain high level of 25 kHzalternating charge current. The power source in the implant is thecapacitor C1. The capacitor C3 is a high frequency decoupling capacitor.The resistor named LOAD is the fictive load of the power source in theimplant. The voltage over the power source, Y5, is also shown in thediagram of FIG. 5 together with the power graph Y9.

The voltage Y3 in the diagram of FIG. 6 is a stabilized voltage at about4.8V used to power the operational amplifier X1. The Y3 voltage isstabilized by a fairly standard linear voltage regulator consisting ofthe MosFet X2, zenerdiode D5, capacitor C4 and resistor R3. Thecapacitor C2 is a high frequency decoupling capacitor. In the diagram ofFIG. 6 the input voltage to the regulator is seen as Y5 and the outputvoltage is Y3.

The X1 operational amplifier is used to amplify the energy balancesignal together with R6 and R7 that set the gain of the amplifiercircuit to 10 times. The input signals to the circuit are shown in thediagram of FIG. 7. Y4 is fixed at a more or less constant level ofapproximately 2.74V by the zenerdiode D1. The voltage Y4 is shunted andhigh frequency filtered by the capacitor C5. A part of the DC voltage atY4 is coupled into the Y2 voltage by the resistor R8 in order to centerthe Y1 output voltage at 2.5V when energy is balanced. The voltage Y2 isbasically the same voltage as the voltage, Y6, over R1, only slightlyhigh frequency filtered by R9 and C7 and shifted in DC level by thecurrent going through R8. To compare Y6 and Y2 look in the diagram ofFIG. 7.

The energy balance output signal of the circuit, Y1 in the diagram ofFIG. 8, also closely correspond to the Y6 voltage. The Y1 voltage is anamplified, 10 times, and DC shifted to center around 2.5V instead of 0Vversion of the Y6 voltage. The higher signal level at Y1 and the DCcenter point around 2.5V is much easier to interface to for the circuitsconnected to the energy balance output signal.

The diagram of FIG. 9 shows the relationship between the energy balancesignal Y1 and the actual voltage over the power source of the implant.The energy balance signal is the derivative of the voltage level overthe power source, Y5. When the energy balance signal, Y1, is negativerelative to 2.5V the voltage level, Y5, drops off and when the energybalance signal is positive relative to 2.5V the Y5 voltage increases.The more negative or positive relative to 2.5V the energy balance signalY1 is the more rapidly the Y5 voltage over the power source increases ordecreases.

The diagram of FIG. 10, of another circuit condition, perhaps even moreclearly shows how the energy balance signal corresponds to thederivative of the Y5 voltage over the power source. The traces shows asituation where the energy put into the power source is held at aconstant level and the load is varied between 5 mA and 30 mA in fourdiscrete steps. During the first 25 ms the load is 30 mA, the following25 ms it is 5 mA then followed by the same 30 mA and 5 mA sequence. Whenthe Y5 voltage over the power source decreases at a constant level dueto the 30 mA load the derivative level is at a constant level below 2.5Vand when the Y5 voltage increases the derivative voltage is positive ata constant level.

The two diagrams of FIG. 11 show the relation ship between the energybalance signal Y1 and the energy imbalance in the circuit in a complexsituation where both the load is varied and the amount of power put intothe implant is varied. The two traces in the first diagram of FIG. 11shows the charging current into the power source and the load current.The charging current is represented by the IY12 trace and the loadcurrent is the IY10 trace. The second diagram of FIG. 11 shows the Y1voltage generated by the altering currents shown in the first diagram.When the amount of stored energy in the power source is changed due tothe energy imbalance the derivative signal Y1 rapidly responds to theimbalance as shown in the diagram.

In a system where the energy balance signal is used as a feedback signalto an external power transmitter, enabling it to regulate thetransmitted power according to the energy imbalance, it is possible tomaintain an optimal energy balance and to keep the efficiency atmaximum. The diagram of FIG. 12 shows the charging current into thepower source and the load current, the charging current are representedby the IY12 trace and the load current is the IY10 trace, as well as thevoltage level over the power source, Y5, and the energy balance signalY1 in such a system. It can clearly be seen that this system rapidlyresponds to any load current changes by increasing the charging current.Only a small spike in the energy balance signal can be seen right at theedges where the load is rapidly changed due to the finite bandwidth ofthe feedback loop. Apart from those small spikes the energy is kept inperfect balance.

FIGS. 13a-13c schematically illustrate different states of operation ofa generally designed apparatus according to one embodiment, when theapparatus is applied on a wall portion of a bodily organ designated BO.The apparatus includes a constriction device and a stimulation device,which are designated CSD, and a control device designated CD forcontrolling the constriction and stimulation devices CSD. FIG. 9a showsthe apparatus in an inactivation state, in which the constriction devicedoes not constrict the organ BO and the stimulation device does notstimulate the organ BO. FIG. 13b shows the apparatus in a constrictionstate, in which the control device CD controls the constriction deviceto gently constrict the wall portion of the organ BO to a constrictedstate, in which the blood circulation in the constricted wall portion issubstantially unrestricted and the flow in the lumen of the wall portionis restricted. FIG. 13c shows the apparatus in a stimulation state, inwhich the control device CD controls the stimulation device to stimulatedifferent areas of the constricted wall portion, so that almost theentire wall portion of the organ BO contracts (thickens) and closes thelumen.

FIGS. 13d and 13e show how the stimulation of the constricted wallportion can be cyclically varied between a first stimulation mode, inwhich the left area of the wall portion (see FIG. 13d ) is stimulated,while the right area of the wall portion is not stimulated, and a secondstimulation mode, in which the right area of the wall portion (see FIG.13e ) is stimulated, while the left area of the wall portion is notstimulated, in order to maintain over time satisfactory bloodcirculation in the constricted wall portion.

It should be noted that the stimulation modes shown in FIGS. 13d and 13eonly constitute a principle example of how the constricted wall portionof the organ BO may be stimulated. Thus, more than two different areasof the constricted wall portion may be simultaneously stimulated incycles or successively stimulated. Also, groups of different areas ofthe constricted wall portion may be successively stimulated.

FIGS. 13f-13h illustrate different states of operation of a modificationof the general embodiment shown in FIGS. 13a-13e , wherein theconstriction and stimulation devices CSD include several separateconstriction/stimulation elements, here three elements CSDE1, CSDE2 andCSDE3. FIG. 13f shows how the element CSDE1 in a first state ofoperation is activated to both constrict and stimulate the organ BO, sothat the lumen of the organ BO is closed, whereas the other two elementsCSDE2 and CSDE3 are inactivated. FIG. 13g shows how the element CSDE2 ina second following state of operation is activated, so that the lumen ofthe organ BO is closed, whereas the other two elements CSDE1 and CSDE3are inactivated. FIG. 13h shows how the element CSDE3 in a followingthird state of operation is activated, so that the lumen of the organ BOis closed, whereas the other two elements CSDE1 and CSDE2 areinactivated. By shifting between the first, second and third states ofoperation, either randomly or in accordance with a predeterminedsequence, different portions of the organ can by temporarily constrictedand stimulated while maintaining the lumen of the organ closed, wherebythe risk of injuring the organ is minimized. It is also possible toactivate the elements CSDE1-CSDE3 successively along the lumen of theorgan to move fluids and/or other bodily matter in the lumen.

FIGS. 13i-13k illustrate an alternative mode of operation of themodification of the general embodiment. Thus, FIG. 13i shows how theelement CSDE1 in a first state of operation is activated to bothconstrict and stimulate the organ BO, so that the lumen of the organ BOis closed, whereas the other two elements CSDE2 and CSDE3 are activatedto constrict but not stimulate the organ BO, so that the lumen of theorgan BO is not completely closed where the elements CSDE2 and CSDE3engage the organ BO. FIG. 13j shows how the element CSDE2 in a secondfollowing state of operation is activated to both constrict andstimulate the organ BO, so that the lumen of the organ BO is closed,whereas the other two elements CSDE1 and CSDE3 are activated toconstrict but not stimulate the organ BO, so that the lumen of the organBO is not completely closed where the elements CSDE1 and CSDE3 engagethe organ BO. FIG. 13k shows how the element CSDE3 in a following thirdstate of operation is activated to both constrict and stimulate theorgan BO, so that the lumen of the organ BO is closed, whereas the othertwo elements CSDE1 and CSDE2 are activated to constrict but notstimulate the organ BO, so that the lumen of the organ BO is notcompletely closed where the elements CSDE1 and CSDE2 engage the organBO. By shifting between the first, second and third states of operation,either randomly or in accordance with a predetermined sequence,different portions of the organ can by temporarily stimulated whilemaintaining the lumen of the organ closed, whereby the risk of injuringthe organ is reduced. It is also possible to activate the stimulation ofthe elements CSDE1-CSDE3 successively along the lumen of the organ BO tomove fluids and/or other bodily matter in the lumen.

FIGS. 14-16 show basic components of an embodiment of the apparatus forcontrolling a flow of fluid and/or other bodily matter in a lumen formedby a tissue wall of a patient's organ. The apparatus comprises a tubularhousing 1 with open ends, a constriction device 2 arranged in thehousing 1, a stimulation device 3 integrated in the constriction device2, and a control device 4 (indicated in FIG. 16) for controlling theconstriction and stimulation devices 2 and 3. The constriction device 2has two elongate clamping elements 5, 6, which are radially movable inthe tubular housing 1 towards and away from each other between retractedpositions, see FIG. 15, and clamping positions, see FIG. 16. Thestimulation device 3 includes a multiplicity of electrical elements 7positioned on the clamping elements 5, 6, so that the electricalelements 7 on one of the clamping elements 5, 6 face the electricalelements 7 on the other clamping element. Thus, in this embodiment theconstriction and stimulation devices form a constriction/stimulationunit, in which the constriction and stimulation devices are integratedin a single piece.

The constriction and stimulation devices may also be separate from eachother. In this case, a structure may be provided for holding theelectrical elements 7 in a fixed orientation relative to one another.Alternatively, the electrical elements 7 may include electrodes that areseparately attached to the wall portion of the patient's organ.

FIG. 17a shows an example of transmitted pulses, according to oneembodiment. The pulses have a constant frequency and amplitude. However,the relation between the times t1 and t2 varies.

FIG. 17b shows another example of transmitted pulses, according toanother embodiment. During the time t1 a train of pulses is transmitted,and during the time t2 no pulses are transmitted. The pulses have aconstant frequency and amplitude. However, the relation between thetimes t1 and t2 varies.

1-286. (canceled)
 287. An apparatus configured to control transmissionof wireless energy supplied to an electrically operable medical deviceadapted to be implanted in a mammal patient, comprising: an externalenergy source adapted to be located outside the mammal patient andcomprising an external control unit, the external energy source beingadapted to transmit wireless energy, an internal energy receiver locatedinside the patient and comprising an internal control unit, the internalenergy receiver being adapted to receive the wireless energy, theinternal energy receiver being configured to directly or indirectlysupply wirelessly received energy to the electrically operable medicaldevice, and a control unit comprising the internal control unit or theexternal control unit, wherein the electrically operable medical deviceis adapted to transfer control information to the control unit, thecontrol information being related to an energy adapted for operating themedical device and said control information being adapted to be used tocontrol the receipt of energy, wherein the apparatus is configured toreceive the wireless energy based on an energy balance being determinedbased on repeatedly detecting a direction and rate of change in acurrent amount of accumulated energy in the internal energy receiver.288. The apparatus according to claim 287, wherein the apparatus isadapted to determine an energy balance, during the transmission ofwireless energy, between the energy received by the internal energyreceiver and energy used for the medical device by at least one of theinternal control unit or the external control unit, and wherein theapparatus is adapted to control the transmission of wireless energy fromthe external energy source based on the determined energy balance. 289.The apparatus according to claim 288, wherein the apparatus is adaptedto detect at least one of a change in said energy balance, such that thetransmission of wireless energy is then controlled based on saiddetected energy balance change, and a difference between energy receivedby said internal energy receiver and energy used for the medical device,such that the apparatus is adapted to control transmission of wirelessenergy based on said detected energy difference.
 290. The apparatusaccording to claim 289, wherein the apparatus is adapted to control theamount of transmitted wireless energy to be at least one of: decreased,when at least one of; the detected energy balance change implies thatthe energy balance is increasing, the detected energy difference impliesthat the received energy is greater than the used energy, the directionof change in the current amount of accumulated energy implies that thereceived energy is greater than the used energy, and the detected energybalance rate implies that the received energy rate is greater than theused energy rate, and increased when at least one of: the detectedenergy balance change implies that the energy balance is decreasing, thedetected energy difference implies that the received energy is less thanthe used energy, the direction of change in the current amount ofaccumulated energy implies that the received energy is greater than theused energy, and the detected energy rate implies that the receivedenergy is less than the used energy.
 291. The apparatus according toclaim 290, wherein the decrease/increase of energy transmissioncorresponds to at least one of: a detected change rate of said detectedenergy difference, direction of change of said detected energydifference, and a magnitude of said detected energy difference.
 292. Theapparatus according to claim 289, wherein the wirelessly received energyused by the medical device is at least one of: consumed to operate themedical device, stored in at least one energy storage device of themedical device and consumed to operate the medical device, and stored inat least one energy storage device of the medical device.
 293. Theapparatus according to claim 292, wherein substantially all energy usedby the medical device is consumed to operate the medical device. 294.The apparatus according to claim 292, wherein substantially all energyused for the medical device is stored in said at least one energystorage device.
 295. The apparatus according In claim 292, wherein theenergy used for the medical device is partly consumed to operate themedical device and partly stored in said at least one energy storagedevice.
 296. The apparatus according to claim 292, wherein a capacitoris provided in the at least one stabilizing unit to stabilize the energyreceived before the energy is supplied directly or indirectly to themedical device.
 297. The apparatus according to claim 289, wherein theapparatus is adapted to directly or indirectly measure the differencebetween the total amount of energy received by the internal energyreceiver and the total amount of consumed, stored or consumed and storedenergy over time, and to determine the energy balance based on adetected change in said difference.
 298. The apparatus according toclaim 287, wherein the apparatus is adapted to determine the energybalance based on a detected range followed over time in the amount ofconsumed and/or stored energy.
 299. The apparatus according to claim297, wherein the apparatus is adapted to detect the change in the amountof consumed, stored or consumed and stored energy by determining overtime a derivative of a measured electrical parameter related to saidamount of consumed, stored or consumed and stored energy, a derivativeat a first given moment is corresponding to the rate of a change at thefirst given moment, wherein the rate of change includes the directionand speed of the change.
 300. The apparatus according to claim 299,wherein the apparatus is adapted to determine said derivative based on adetected rate of change of the electrical parameter.
 301. The apparatusaccording to claim 287, wherein the apparatus is adapted to supplyenergy received by the internal energy receiver to the medical devicewith at least one of: at least one constant voltage, wherein theconstant voltage is created by a constant voltage circuitry comprised inthe apparatus, and at least one constant current, wherein the constantcurrent is created by a constant current circuitry comprised in theapparatus.
 302. The apparatus according to claim 289, wherein saiddetected difference relates to an integral over time of at least onemeasured electrical parameter related to said energy balance, whereinsaid integral of the electrical parameter relates to the energy balanceas an accumulated difference between the total amount of energy receivedby said internal energy receiver and the total amount of consumed and/orstored energy.
 303. The apparatus according to claim 287, wherein theapparatus is adapted to use the direction of change to control thetransmission of wireless energy in at least one of the following ways:decreasing the transmitted energy, when direction of change implies thatthe received energy is greater than the used energy, and increasing thetransmitted energy, when direction of change implies that the usedenergy is greater than the used received energy.
 304. The apparatusaccording to claim 287, wherein the apparatus is adapted to use a rateof change corresponding to the speed of change to control thetransmission of wireless energy in at least one of the following ways:decreasing the transmitted energy in a small step, when speed of changeis smaller, and direction of change implies that the received energy isgreater than the used energy, decreasing the transmitted energy in alarger step, when speed of change is larger, and direction of changeimplies that the received energy is greater than the used energy,increasing the transmitted energy in a small step, when speed of changeis smaller, and direction of change implies that the used energy isgreater than the used received energy, and increasing the transmittedenergy in a larger step of the speed of change is implies a larger speedof, when speed of change is larger, and direction of change implies thatthe energy is greater than the used received energy.
 305. The apparatusaccording to claim 287, further comprising at least one stabilizing unitadapted to stabilize the wirelessly received energy in the electricallyoperable medical device, wherein the electrically operable medicaldevice is adapted to consume, store or consume and store the wirelesslyreceived energy after it has been stabilized in the at least onestabilizing unit of the electrically operable medical device, whereinthe rate of change is a speed of change of the energy balance measuredas at least one electrical parameter related to accumulated energy inthe stabilizing unit, wherein the control information is further relatedto the direction and speed of change in the current amount ofaccumulated energy in the at least one energy stabilizing unit.
 306. Theapparatus according to claim 299, further adapted to supply the energywith at least one of: at least two different voltages, including the atleast one constant voltage, and at least two different currents,including said at least one constant current.